Granulate composition of antiblocking agents and additives for polymer production

ABSTRACT

The invention comprises a granulate comprising a) a micronized silicic acid gel (A) with an average particle size from 2 to 15 microns, a specific pore volume from 0.3 to 2.0 ml/g, a specific surface (BET) from 200 to 1000 m 2 /g, in a concentration from 5 to 60% by weight or b) a hydrated or dehydrated aluminosilicate (B) which contains sodium and/or potassium and/or calcium cations, with a particle size between 1 and 25 microns in a concentration from 5 to 75% by weight and c) an organic additive composition (C) in a concentration from 25 to 95% by weight, but at least 5% more (measured by the oil adsorption process) than that which is necessary to fill all pores of the silicic acid and the spaces between the silicic acid particles and the aluminosilicate and the aluminosilicate particles.

This invention relates to a new type of additive for polymer filmproduction, and especially a granulate which contains

a) one or more additives for polymer film production and

b) a micronized silicic acid or an aluminosilicate.

This granulate is suitable as an additive for example in the processingof polyolefins and the production of polyolefin films.

It is known that in the production of polyolefin films several additivesare necessary to benefit the various properties of the finished films.They are for example

i) antiblocking agents, for example, fine-particle diatomaceous earth,silicic acid, silica gel;

ii) lubricants, such as for example fatty acid amides and especiallyoleic acid amide and erucic acid amide;

iii) primary antioxidants from the group of sterically hindered phenols,secondary aryl amines, etc.;

iv) secondary antioxidants from the group of phosphorus compositions,thioesters, hydroxylamines, etc.;

v) antistatic agents from the group of ammonium salts, glycerin esters,anionic compounds, etc.;

vi) light stabilizers from the group of benzophenones, benzotriazols,“HALS” (“Sterically Hindered Amines Light Stabilizers”), etc.;

vii) flame retardants from the group of halogenated organic compounds,metal hydrates, etc.;

viii) softeners from the group of phthalates, monocarboxylic acidesters, aliphatic dicarboxylic acid esters, etc.

Granulates of pure organic additives are already known. At the same timecombinations of micronized silicic acids or aluminosilicates asantiblocking agents with organic additives cause poor dispersabilitywhen granulation processes according to the prior art are used, forexample, compacting in molds or compacting by nozzles (cold pressing).

Japanese patent HEI 569865 for example describes an additive-pelletcomposition which comprises spherical pellets of amorphoussilicoaluminate and organic additives. Organic components can be forexample lubricants, antistatic agents and softeners, UV stabilizers andantioxidants, etc. This patent application however is not concerned withsynthetic, amorphous silicic acids or with crystalline aluminosilicates.

German patent 33 37 356 describes a combined antiblocking and lubricantconcentrate, a master batch being formed with a polyolefin.

German patent 44 24 775 describes a special antiblocking agent based onsilicon dioxide with a bimodal pore size distribution. This antiblockingagent is combined with lubricants such as oleic acid amid or erucic acidamide to produce polyolefin master batches.

U.S. Pat. No. 5,053,444 describes a polymer concentrate which containsas the additive aluminum oxide or silicon dioxide. Other additives arelubricants, antioxidants, UV stabilizers, antistatic agents, etc.

All these patents show that so far there has been no success inproducing a free-flowing granulate which contains only synthetic,amorphous silicic acid and organic additives and which at the same timecan be easily dispersed in polymers. A certain polymer for forming amaster batch is always contained. This means that the additiveconcentrates cannot be used for just any polymer types.

U.S. Pat. No. 3 266 924 describes production of homogenous mixtures offine particle silicic acid and fatty acid amides in a mixer. The amidesare added to the silicic acid during mixing at a temperature near themelting point of the amides. This yields a powder mixture.

In view of the described defects of known additives, the object was toproduce an additive that is universally suitable for many applicationsand polymers, which can be easily and economically used, and thus hasapplication advantages such as good dispersability with simultaneousoccurrence in granulate form.

As claimed in the invention, this object was achieved by a granulatecomposition which is characterized in that it

a) consists of micronized silicic acid gel (A) with an average particlesize from 2 to 15 microns, preferably 5 to 10 microns, a specific porevolume from 0.3 to 2.0 ml/g, preferably 0.5 to 1.5 ml/g, a specificsurface (BET) from 200 to 1000 m²/g, preferably 200 to 800 m²/g, in aconcentration from 5 to 60% by weight, preferably 10 to 50% by weight,especially 15 to 45% by weight, or

b) a hydrated or dehydrated aluminosilicate (B) which contains sodiumand/or potassium and/or calcium cations, with an average particle sizebetween 1 and 25 microns in a concentration from 5 to 75% by weight,preferably 10 to 60% by weight, especially 15 to 50% by weight, and

c) an organic additive composition (C) in a concentration from 25 to 95%by weight, preferably 40 to 90% by weight, especially 50 to 85% byweight, but at least 5% more (measured by the oil adsorption process)than that which is necessary to fill all the pores of the silicic acidand the spaces between the silicic acid particles and thealuminosilicate particles.

The composition as claimed in the invention has a dispersability inpolymers which is as good as the individual components. The organiccomposition (C) can consist of one or more of the following componentsin any proportion:

i) lubricants from the croup of fatty acid amides;

ii) primary antioxidants from the group of sterically hindered phenols,secondary aryl amines, etc.;

iii) secondary antioxidants from the group of phosphorus compositions,thioesters, hydroxylamines, etc.;

iv) antistatic agents from the group of ammonium salts, glycerin esters,anionic compounds, etc.;

v) light stabilizers from the group of benzophenones, benzotriazols,“HALS” (“Sterically Hindered Amines Light Stabilizers”), etc.;

vi) flame retardants from the group of halogenated organic compounds,metal hydrates, etc.;

vii) softeners from the group of phthalates, monocarboxylic acid esters,aliphatic dicarboxylic acid esters, etc.

It has now been surprisingly found that granulates with micronizedsilicic acid or aluminosilicates lead to good dispersability, if theinorganic components are added to a melt of the organic additives. Thiscan be done by adding the inorganic components to a melt of the organiccomponents produced beforehand or when a premixture of the organic andinorganic components is heated to the melting point of the organiccomponent. The concentration of inorganic components cannot be higherthan the critical pigment volume concentration, i.e. the molten organicphase must be able to fill all empty pores of the silicic acid (in thecase of aluminosilicate the particle pores are too small for the organicmolecules) and the interstices between the organic particles. It isnecessary to have an excess of organic components to achieve a paste orliquid mass. The formation of granulates (pellets) is achieved either byspray drying of the melt or by extrusion of strands with subsequentcomminution. The preferred technical approach is to use an extruder tomelt the organic components and to achieve distribution of inorganicparticles. The discharge of the extruder in the form of strands is cutwith a means of the prior art (“hot knock-off”). Afterwards thegranulate can be cooled, preferably in a fluidized bed, to preventaggregation of the individual particles. Another possibility is that thestrands are guided into a water bath and cut therein. The surface wateris then removed preferably in a fluidized bed.

The advantages of this invention are:

Delivery of all additives in pelletized form with only proportioninginto the extruder.

More precise proportioning of the components.

Processing in the final application does not cause any dust.

Higher bulk density of the pellets than those of the simple physicalmixtures of amorphous silicic acids and additives (and therefore lowertransport and production costs).

Good dispersability of additives in the polymer mass.

EXAMPLES Example 1 Pellets of Silicic Acid and Erucic Amide

A physical mixture of 43% pure amorphous micronized silicic acid(specific pore volume 1.0 ml/g, Malvern median particle size 4.8microns) and 57% erucic amide were proportioned volumetrically into the6th extrusion zone of a Theyson TSK 30 twin screw extruder. The extruderwas operated with a screw rotation speed of 320/min and a throughput of6.3 kg/h. The temperature profile of the extruder was:

Extrusion Measured zone Setpoint temperature/° C. 6 25 36 7 100 99 8 100102 9 80 82 10 20 48 11 20 77

The resulting point was 85° C. The material was pressed through anextruder nozzle with an opening of 4 mm and cooled with air before thestands were cut into pellets by a rotating blade. Dispersability wastested in example 5.

Example 2 Pellets of Silicic Acid and an Additive Composition

A premixture was produced with a 500 l Henschel mixer (type FM 500) bymixing all additives for 2.5 minutes at a rotation speed of 840/min. Thecomposition was as follows:

Amorphous micronized  9.31% silicic acid (specific pore volume 1.0 ml/g;Malvern median particle size 4.8 microns) Erucic amide (Crodamide ER)46.58% Croda Universal Irganox 1010 23.26% Ciba-Geigy(pentaerythrityl(3-(3.5-bis (1,1-dimethylethyl)-4-hydroxyphenyl)propioniate Irgaphos 168 (tris(2,4-di- 17.6% Ciba-Geigytert.butylphenyl)phosphite) Ca stearate type M  8.85% Sogis

This premixture was metered in the first feed zone of the twin screwextruder (type Theyson DN 60) with gravimetric Brabender proportioning(90.2 kg/h). In the 4th extrusion zone an additional amount of 24.3% or29.8 kg/h amorphous silicic acid was added. The resulting finalcomposition was:

Amorphous micronized silicic acid 31.2 (specfic pore volume 1.0 ml/g;Malvern median particle size 4.8 microns) Crodamide ER 35.3% Irqanox1010  9.1% Irgaphos 168 17.6% Ca stearate  6.7%

The Theyson DN 60 extruder was operated with a worm rotation speed of350/min and a total throughput of 120 kg/h and the following temperatureprofile:

Extrusion Measured zone Setpoint temperature/° C. 1 40 41 2 160 122 3160 148 4 140 143 5 95 97 6 78 77 7 75 74 8 83 90 9 83 85 10 180 154 11145 145

The resulting melting point was 147° C.

The extrusion mass was driven through a nozzle plate with 7 holes with a4 mm diameter each on the casting head of the extruder. The extrudatewas guided into the granulator with a water stream. The granulatorconsisted of two rolls for transport of the strands to a rotating blade.The pelletized premixture was then dried and screened in a flow beddrier (air temperature 35° C., residence time 20 seconds) to remove thefine portions (<2 mm) and coarse portions (>6 mm). The total yield was80%. Dispersability is described in example 5.

Example 3 Pellets of Silicic Acid and Lubricant by Compacting ofComponents

A powder mixture was produced from 8.6 kg of micronized silicic acidwith a specific pore volume of 0.95 ml/g, Malvern median particle size 5microns and 11.4 kg erucic amide (Croda Universal Ltd. Hull/GB) by meansof a 100 l Loedige batch mixer. After a mixing time of 3 minutes goodhomogeneity of the mixture and a bulk weight of roughly 300 g/l areachieved.

This powder mixture was metered with a throughput of 40 kg/h in aHosokawa Bepex Compactor L 200/50 P. In this machine the powder waspressed between two compact particles with a 12 mm profile and with acompacting force of roughly 30 kN. Using the Hosokawa Bepex device thenparticles from 1 to 3 mm average size were achieved. The bulk densitywas increased from 300 g/l (for the powder mixture) to 520 g/l forpellets. These granulates were then supplied to a 300 mm twin screwextruder as in Example 1 in order to produce a polypropylene masterbatch with 5% by weight based on the silicic acid content. The resultsof the dispersability tests are given in FIG. 5.

Example 4 Comparison Example with Antiblocking Agents and Lubricants asPowder Via a Master Batch

A master batch was produced from polypropylene (Solvay DV 001PF) and amixture consisting of 43% pure amorphous silicic acid (specific porevolume 1.0 ml/g Malvern median particle size micron) and 57% erucic acidamide. The total concentration of the mixture was 5% by weight or 60g/h. A twin screw extruder (Theyson TSK 30/40D) was used for production.The polypropylene power was metered into the first extrusion zone, themixture of silica-erucic acid amide into the third extrusion zone. Theextrusion conditions were as follows:

Screw rotation speed 300 1/min Extruder screen 200 mesh Nozzle openingdiameter  4 mm Number of openings  2 Throughput  12 kg/h Temperatureprofile (setting values) Zone 1 Cooling Zone 2 250° C. Zone 3 250° C.Zone 4 230° C. Zone 5 220° C. Zone 6 220° C. Zone 7 210° C. Zone 8 200°C. Zone 9 200° C. Zone 10 190° C. Temperature of screen changer Zone 1200° C. Zone 2 200° C. Nozzle temperature 210° C.

The extruded strands with a diameter of 4 mm were cooled in a water bathand then granulated in a granulator (strand granulator series 750/l)from Theyson. The dispersability is described in example 5.

Example 5 Dispersability

Dispersability tests were run to determine the quality of thedispersability of the silicic acid in the polyolefins. The compositionswith silicic acid which were used as produced according to examples 1 to4 in order to produce polypropylene film roughly 30 microns thick [sic].

On a twin screw extruder (Theyson TSK 30/40D) a master batch inpolypropylene (Solvay HV 001PF) with an additive composition is producedin concentrations such that 5% by weight silicic acid were achieved. Thepolypropylene powder was metered into the first extrusion zone, theadditive composition into the third extrusion zone. Extrusion conditionswere as follows:

Worm rotation speed 300 1/min Extruder screen 200 mesh Nozzle openingdiameter  4 mm Number of openings  2 Throughput  12 kg/h Temperatureprofile (setting values) Zone 1 Cooling Zone 2 250° C. Zone 3 250° C.Zone 4 230° C. Zone 5 220° C. Zone 6 220° C. Zone 7 210° C. Zone 8 200°C. Zone 9 200° C. Zone 10 190° C. Temperature of screen changer Zone 1200° C. Zone 2 200° C. Nozzle temperature 210° C.

The extruded strands with a diameter of 4 mm were cooled in a water bathand then granulated in a granulator (strand granulator series 750/l).

A Kiefel extruder was used to produce a Gast polypropylene film with asilicic acid concentration of 2000 ppm. The master batch producedbeforehand was diluted with polypropylene (Mantel K 6100) up to thedesired concentration of 2000 pm. A film 40 microns thick was used inorder to determine the number of “nibs” (undispersed silicic acidparticles) compared to a blank trial without silicate particles.

Nibs >0.5 mm diameter were counted on a 20×5 cm sheet and then thevalues transferred to 1 m².

The evaluation was done against a standardized film series. Thedispersability standards were assessed as follows:

Characteristic 1=very good, almost no surface faults

Characteristic 2=acceptable, few faults

Characteristic 3=not acceptable, several surface faults

Characteristic 4=poor, film surface is oversaturated with faults.

The film patterns which were produced from the additive composition withsilicic acid as described in examples 1 to 4, led to the followingresults according to the evaluation:

Example number Characteristic No. of “nibs”/m² 1 1 300 2 1 200 34 >80000 4 1 600 Blank trial 1 200

With respect to general use of the invention the contents of individualadditives can vary widely. The concentration limits for some of thespecially named additives in the granulate are preferably as follows:

Silicic acid: 20-41% by weight

Crodamide ER: 20-40% by weight

Irganox 1010: 5-20% by weight

Irgafos 168: 10-25% by weight

Ca-Stearate type M: 2-12% by weight

The specific pore volume of the silicic acid was determined according tonitrogen sorption measurement with surface and pore volume measurementdevice ASAP 2400 from Fa. Micromeritics. The basis of this method isthat porous solids such as silicic acid can adsorb gas molecules intheir cavities. Conclusions can be drawn for the specific surface SA(m2/) and the specific pore volume PV (ml/g) from the plot of the amountof adsorbed gas (at a defined temperature) against pressure over thesample. In the ASAP 2400 the adsorbed amount of nitrogen is determinedvolumetrically as a function of the equilibrium partial pressure p/p0 ata temperature of 77° K. on the activated sample.

With respect to the state of filling of the pores and cavities,reference is made to the oil adsorption method which enables access tothe critical pigment volume concentration. It is based on DIN EN ISO787, Part 5. When the pores and cavities are overfilled a transitionfrom powder to paste-like mass takes place with embedding of the porousparticles.

Tabulation of example “Inventions versus prior art” Example DescriptionStatus Delineation to other examples No. 1 silicic acid InventionProduction by extrusion on lab. scale and erucic two additives in finaluse 100% active *1) acid amide good dispersability in polymer (see Ex.5) pellets *2) Product advantages: no dust, good flow property, etc. No.2 Pellets of Invention Production by extrusion on production scalesilicic acid all 5 additives in final use 100% active *1) and 4 diff.good dispersability in polymer (see Ex. 5) additives Product advantages:no dust, good flow property, etc. No. 3 silicic acid Prior art Granulateproduction with current compaction process and erucic two additives infinal use 100% active *1) acid amide poor dispersability in polymer (seeEx. 5) pellets *2) Product advantages: no dust, good flow property, etc.No. 4 silicic acid Prior art Powder mixture production with currentmixer and erucic Blank two additives in final use 100% active *1) acidamide trial good dispersability in polymer (see Ex. 5) powder No productadvantages: dust development, poor flow mixture *2) properties, etc. No.5 Application-engineering test process for assessing product quality(dispersability) of examples 1-4 *1) No polymer or wax were used forpellet production (all components are active) *2) all formulations(example no. 1, 3, 4) are identical

What is claimed is:
 1. A process for producing granulated productscomprising 1) selecting a member of the group consisting of a)micronized silicic acid gel (A) with an average particle size from 2 to15 microns, a specific pore volume from 0.3 to 2.0 ml/g, and a specificsurface (BET) from 200 to 1000 m²/g; b) hydrated or dehydratedaluminosilicate (B) which contains sodium and/or potassium and/orcalcium cations, with a particle size between 1 and 25 microns; andmixtures of a) and b); 2) combining the member of 1) with an organicadditive composition (C) in an amount of about 25 to about 95% by weightof the total composition, but using a volume which is at least 5% more(measured by the oil adsorption process) than that which is necessary tofill all pores of any silicic acid and the spaces between silicic acidparticles and/or aluminosilicate particles; (3) heating the combinationof 2) to a melting temperature of organic additive (C); (4) extrudingthe melted composition resulting from step (3) and (5) granulating theextruded material from (4).
 2. Process of claim 1 wherein the componentsof (A), (B) and/or (C) are supplied separately to an extruder. 3.Process of claim 1 wherein a premixture of components of (A), (B) and/or(C) is supplied to an extruder and subsequently granulated.
 4. A processof claim 1 wherein the extruded composition from (4) is granulatedduring (5) into particles and those particles are subsequently cooled ina fluidized bed.
 5. A process of claim 1 wherein the extrudedcomposition from (4) is granulated during (5) in water and the water issubsequently atomized in a fluidized bed.
 6. Process of claim 1, whereinthe organic additive (C) comprises one or more of the followingcomponents: i) lubricants from the group of fatty acid amides; ii)primary antioxidants from the group of sterically hindered phenols,secondary aryl amines; iii) secondary antioxidants from the group ofphosphorus compositions, thioesters, hydroxylamines; iv) antistaticagents from the group of ammonium salts, glycerin esters, anioniccompounds; v) light stabilizers from the group of benzophenones,benzotriazols, sterically hindered amine light stabilizers; vi) flameretardants selected from the group consisting of halogenated organiccompounds, metal hydrates, and mixtures of the same; vii) softenersselected from the group consisting of phthalates, monocarboxylic acidesters, and aliphatic dicarboxylic acid esters.